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Interferometric Studies of Laser-Created Plasmas Using Compact Soft X-Ray Lasers (open access)

Interferometric Studies of Laser-Created Plasmas Using Compact Soft X-Ray Lasers

We summarize results of several successful dense plasma diagnostics experiments realized by combining two different kinds of table-top soft x-ray lasers with an amplitude division interferometer based on diffraction grating beam splitters. In the first set of experiments this robust high throughput diffraction grating interferometer (DGI) was used with a 46.9 nm portable capillary discharge laser to study the dynamics of line focus and point focus laser-created plasmas. The measured electron density profiles, which differ significantly from those expected from a classical expansion, unveil important two-dimensional effects of the dynamics of these plasmas. A second DGI customized to operate in combination with a 14.7 nm Ni-like Pd transient gain laser was used to perform interferometry of line focus laser-created plasmas with picosecond time resolution. These measurements provide valuable new benchmarks for complex hydrodynamic codes and help bring new understanding of the dynamics of dense plasmas. The instrumentation and methodology we describe is scalable to significantly shorter wavelengths, and constitutes a promising scheme for extending interferometry to the study of very dense plasmas such as those investigated for inertial confinement fusion.
Date: December 4, 2003
Creator: Dunn, J.; Nilsen, J.; Moon, S.; Keenan, R.; Jankowska, E.; Maconi, M. C. et al.
System: The UNT Digital Library
Effect of Structural Modification on Second Harmonic Generation in Collagen (open access)

Effect of Structural Modification on Second Harmonic Generation in Collagen

The effects of structural perturbation on second harmonic generation in collagen were investigated. Type I collagen fascicles obtained from rat tails were structurally modified by increasing nonenzymatic cross-linking, by thermal denaturation, by collagenase digestion, or by dehydration. Changes in polarization dependence were observed in the dehydrated samples. Surprisingly, no changes in polarization dependence were observed in highly crosslinked samples, despite significant alterations in packing structure. Complete thermal denaturation and collagenase digestion produced samples with no detectable second harmonic signal. Prior to loss of signal, no change in polarization dependence was observed in partially heated or digested collagen.
Date: April 4, 2003
Creator: Stoller, P C; Reiser, K M; Celliers, P M & Rubenchik, A M
System: The UNT Digital Library
High Current Ion Source Development for Heavy Ion Fusion (open access)

High Current Ion Source Development for Heavy Ion Fusion

We are developing high-current-density high-brightness sources for Heavy Ion Fusion applications. Heavy ion driven inertial fusion requires beams of high brightness in order to achieve high power density at the target for high target gain. At present, there are no existing ion source types that can readily meet all the driver HIF requirements, though sources exist which are adequate for present experiments and which with further development may achieve driver requirements. Our two major efforts have been on alumino-silicate sources and RF plasma sources. Experiments being performed on a 10-cm alumino-silicate source are described. To obtain a compact system for a HIF driver we are studying RF plasma sources where low current beamlets are combined to produce a high current beam. A 80-kV 20-{micro}s source has produced up to 5 mA of Ar{sup +} in a single beamlet. The extraction current density was 100 mA/cm{sup 2}. We present measurements of the extracted current density as a function of RF power and gas pressure, current density uniformity, emittance, and energy dispersion (due to charge exchange).
Date: September 4, 2003
Creator: Westenskow, G A; Grote, D P & Kwan, J W
System: The UNT Digital Library
Science and Technology in Support of U.S. Policy in Central Asia (open access)

Science and Technology in Support of U.S. Policy in Central Asia

The current war with Iraq, international interventions in Afghanistan, and the continuous and seemingly insolvable problems in the Middle East emphasize the importance of supporting stable, healthy countries throughout the Middle East and South and Central Asia. The political alliances and foreign aid promulgated by the Cold War have been seriously strained, creating a more uncertain and unstable international environment. We must stay engaged with this part of the world. New partnerships must be forged. Central Asia represents a mix of political systems - from totalitarian rule to nascent democracy; of economic resources from natural to human; and of cultures from ancient to modern - making it of strategic importance to U. S. national and economic security. The U.S. must remain committed and proactively engaged in the region to promote open and democratic societies attractive to outside investment and to prevent the proliferation of weapons of mass destruction and extremist groups. The U.S is admired for its science and technology and its flexibility in innovation and applying S&T to solve problems. The inherent value that S&T can contribute to advancing U.S. policy goals is the underlying assumption of this report. Science and technology and their applications have much to contribute …
Date: November 4, 2003
Creator: Knapp, R B
System: The UNT Digital Library
A fast inversion method for interpreting borehole electromagnetic data (open access)

A fast inversion method for interpreting borehole electromagnetic data

None
Date: March 4, 2003
Creator: Kim, Hee Joon; Lee, Ki Ha & Wilt, Michael
System: The UNT Digital Library
Effect of ion mass and charge state on transport of vacuum ARC plasmas through a biased magnetic filter (open access)

Effect of ion mass and charge state on transport of vacuum ARC plasmas through a biased magnetic filter

The effect of ion mass and charge state on plasma transport through a 90{sup o}-curved magnetic filter is experimentally investigated using a pulsed cathodic arc source. Graphite, copper, and tungsten were selected as test materials. The filter was a bent copper coil biased via the voltage drop across a low-ohm, ''self-bias'' resistor. Ion transport is accomplished via a guiding electric field, whose potential forms a ''trough'' shaped by the magnetic guiding field of the filter coil. Evaluation was done by measuring the filtered ion current and determination of the particle system coefficient, which can be defined as the ratio of filter ion current, divided by the mean ion charge state, to the arc current. It was found that the ion current and particle system coefficient decreased as the mass-to-charge ratio of ions increased. This result can be qualitatively interpreted by a very simply model of ion transport that is based on compensation of the centrifugal force by the electric force associated with the guiding potential trough.
Date: September 4, 2003
Creator: Byon, Eungsun; Kim, Jong-Kuk; Kwon, Sik-Chol & Anders, Andre
System: The UNT Digital Library
Regional cooperation in energy efficiency standard-setting and labeling in North America (open access)

Regional cooperation in energy efficiency standard-setting and labeling in North America

The North American Energy Working Group (NAEWG) was established in 2001 by the governments of Canada, Mexico, and the United States. The goals of NAEWG are to foster communication and cooperation on energy-related matters of common interest, and to enhance North American energy trade and interconnections consistent with the goal of sustainable development, for the benefit of all three countries. At its outset, NAEWG established teams to address different aspects of the energy sector. One, the Energy Efficiency Expert Group, undertook activity in three areas: (1) analyzing commonalities and differences in the test procedures of Canada, Mexico, and the United States, and identifying specific products for which the three countries might consider harmonization; (2) exploring possibilities for increased mutual recognition of laboratory test results; and (3) looking at possibilities for enhanced cooperation in the Energy Star voluntary endorsement labeling program. To support NAEWG's Expert Group on Energy Efficiency (NAEWG-EE), USDOE commissioned Lawrence Berkeley National Laboratory, representing the Collaborative Labeling and Appliance Standards Program (CLASP), to prepare a resource document comparing current standards, labels, and test procedure regulations in Canada, Mexico, and the United States. The resulting document identified 46 energy-using products for which at least one of the three countries …
Date: August 4, 2003
Creator: Wiel, Stephen & Van Wie McGrory, Laura
System: The UNT Digital Library
The role of oxygen at screw dislocations in GaN (open access)

The role of oxygen at screw dislocations in GaN

None
Date: September 4, 2003
Creator: Arslan, Ilke & Browning, Nigel D.
System: The UNT Digital Library
The Advanced Light Source Upgrade (open access)

The Advanced Light Source Upgrade

The ALS, a third-generation synchrotron light source at Berkeley Lab, has been operating for almost a decade and is generating forefront science by exploiting the high brightness of a third-generation source in three areas: (1) high resolving power for spectroscopy; (2) high spatial resolution for microscopy and spectromicroscopy; and (3) high coherence for experiments such as speckle. However, the ALS was one of the first third-generation machines to be designed, and accelerator and insertion-device technology have significantly changed since its conception. As a result, its performance will inevitably be outstripped by newer, more advanced sources. To remain competitive and then set a new standard, the performance of the ALS, in particular its brightness, must be enhanced. Substantial improvements in brightness and current have always been feasible in principle, but they incur the penalty of a much reduced lifetime, which is totally unacceptable to our users. Significant brightness improvements can be realized in the core soft x-ray region by going to top-off operation, where injection would be quasi-continuous and the lifetime objections disappear. In top-off mode with higher average current, a reduced vertical emittance and beta function, and small-gap permanent-magnet or superconducting insertion devices, one to two orders of magnitude improvement …
Date: November 4, 2003
Creator: Chemla, Daniel S.; Feinberg, Benjamin; Hussain, Zahid; Krebs, Gary F.; Padmore, Howard A.; Robin, David S. et al.
System: The UNT Digital Library
Searches for new physics at D0 (open access)

Searches for new physics at D0

The integrated luminosity at Run 2 of the Tevatron is approaching the Run 1 total, and data analysis is progressing. New results in searches for new physics by the D0 experiment are presented in a variety of channels, demonstrating good performance of the detector and detailed understanding of the data.
Date: June 4, 2003
Creator: Brooijmans, Gustaaf
System: The UNT Digital Library
Fermilab booster modeling and space charge study (open access)

Fermilab booster modeling and space charge study

The Fermilab Booster is a bottleneck limiting the proton beam intensity in the accelerator complex. A study group has been formed in order to have a better understanding of this old machine and seek possible improvements. The work includes lattice modeling, numerical simulations, bench measurements and beam studies. Based on newly obtained information, it has been found that the machine acceptance is severely compromised by the orbit bump and dogleg magnets. This, accompanied by emittance dilution from space charge at injection, is a major cause of the large beam loss at the early stage of the cycle. Measures to tackle this problem are being pursued.
Date: June 4, 2003
Creator: al., Weiren Chou et
System: The UNT Digital Library
Lattice function measurements of the Fermilab recycler ring (open access)

Lattice function measurements of the Fermilab recycler ring

The Fermilab Recycler ring, designed and built as an 8-GeV anti-proton storage ring, is at the final stage of its commissioning. Once integrated into the accelerator complex it is expected to help achieve the luminosity goal of Run II at Fermilab. The Recycler Ring is made up mostly of combined function magnets with a substantial sextupole component. Any orbit error could cause higher order feed-down and potentially change the machine. Lattice function measurements had been taken at various stages of the machine and the results are presented here.
Date: June 4, 2003
Creator: Yang, Ming-Jen; Marchionni, Alberto & Mishra, Shekhar
System: The UNT Digital Library
Barrier RF stacking at Fermilab (open access)

Barrier RF stacking at Fermilab

A key issue to upgrade the luminosity of the Tevatron Run2 program and to meet the neutrino requirement of the NuMI experiment at Fermilab is to increase the proton intensity on the target. This paper introduces a new scheme to double the number of protons from the Main Injector (MI) to the pbar production target (Run2) and to the pion production target (NuMI). It is based on the fact that the MI momentum acceptance is about a factor of four larger than the momentum spread of the Booster beam. Two RF barriers--one fixed, another moving--are employed to confine the proton beam. The Booster beams are injected off-momentum into the MI and are continuously reflected and compressed by the two barriers. Calculations and simulations show that this scheme could work provided that the Booster beam momentum spread can be kept under control. Compared with slip stacking, a main advantage of this new method is small beam loading effect thanks to the low peak beam current. The RF barriers can be generated by an inductive device, which uses nanocrystal magnet alloy (Finemet) cores and fast high voltage MOSFET switches. This device has been designed and fabricated by a Fermilab-KEK-Caltech team. The first …
Date: June 4, 2003
Creator: al., Weiren Chou et
System: The UNT Digital Library
Amorphous and nanocrystalline Mg{sub 2}Si thin film electrodes (open access)

Amorphous and nanocrystalline Mg{sub 2}Si thin film electrodes

Mg{sub 2}Si films, prepared by pulsed laser deposition (PLD), were amorphous, as prepared, and nanocrystalline following annealing. Their micro-structure and electrochemical characteristics were studied by high resolution transmission electron microscopy (HRTEM) and electrochemical cycling against lithium. HRTEM analysis revealed that some excess Si was present in the films. The more amorphous thinner film exhibited excellent cyclability. However, when the film becomes crystalline, the irreversible capacity loss was more significant during the initial cycling and after *50 cycles. Interpretations of the superior stability of the amorphous films are examined.
Date: February 4, 2003
Creator: Song, Seung-Wan; Striebel, Kathryn A.; Song, Xiangyun & Cairns, Elton J.
System: The UNT Digital Library
Charm physics at the Tevatron (open access)

Charm physics at the Tevatron

The cross section of p{bar p} into charm is very high compared to e{sup +}e{sup -}-machines, but it is orders of magnitude smaller than the total cross section of {approx} 100mb. This explains the need for a good trigger mechanism. Traditionally charm physics at hadron colliders relies on a lepton signature. For example, the decay of the J{psi} into two leptons or semi-leptonic decays of D-mesons. Both detectors at the Tevatron, CDF and D0 have undergone substantial upgrades for RUN II. CDF now exploits a new trigger technique selecting more abundant hadronic decays. First charm physics results from the CDF and D0 experiments at the Tevatron Run II are presented. With the addition of the Secondary Vertex Trigger CDF has become a competitive charm experiment.
Date: June 4, 2003
Creator: Korn, A.
System: The UNT Digital Library
2 MW upgrade of the Fermilab Main Injector (open access)

2 MW upgrade of the Fermilab Main Injector

In January 2002, the Fermilab Director initiated a design study for a high average power, modest energy proton facility. An intensity upgrade to Fermilab's 120-GeV Main Injector (MI) represents an attractive concept for such a facility, which would leverage existing beam lines and experimental areas and would greatly enhance physics opportunities at Fermilab and in the U.S. With a Proton Driver replacing the present Booster, the beam intensity of the MI is expected to be increased by a factor of five. Accompanied by a shorter cycle, the beam power would reach 2 MW. This would make the MI a more powerful machine than the SNS or the J-PARC. Moreover, the high beam energy (120 GeV) and tunable energy range (8-120 GeV) would make it a unique high power proton facility. The upgrade study has been completed and published. This paper gives a summary report.
Date: June 4, 2003
Creator: Chou, Weiren
System: The UNT Digital Library
Top quark production cross-section at the Tevatron Run 2 (open access)

Top quark production cross-section at the Tevatron Run 2

The top quark pair production cross-section {sigma}{sub t{bar t}} has been measured in p{bar p} collisions at center of mass energies of 1.96 TeV using Tevatron Run 2 data. In the beginning of Run 2 both CDF and D0 {sigma}{sub t{bar t}} measurements in the dilepton channel t{bar t} {yields} WbW{bar b} {yields} {bar {ell}}{nu}{sub {ell}}b{ell}{prime} {bar {nu}}{sub {ell}{prime}}{bar b} and in the lepton plus jets channel t{bar t} {yields} WbW{bar b} {yields} q{bar q}{prime} b{ell}{bar {nu}}{sub {ell}}{bar b} + {bar {ell}}{nu}{sub {ell}}bq{bar q}{prime} {bar b} agree with the NLO (Next-to-Leading-Order) theoretical predictions. The presence of a top signal in Tevatron data has been reestablished.
Date: June 4, 2003
Creator: Cabrera, S.
System: The UNT Digital Library
Application of adaptive mesh refinement to particle-in-cell simulations of plasmas and beams (open access)

Application of adaptive mesh refinement to particle-in-cell simulations of plasmas and beams

Plasma simulations are often rendered challenging by the disparity of scales in time and in space which must be resolved. When these disparities are in distinctive zones of the simulation domain, a method which has proven to be effective in other areas (e.g. fluid dynamics simulations) is the mesh refinement technique. We briefly discuss the challenges posed by coupling this technique with plasma Particle-In-Cell simulations, and present examples of application in Heavy Ion Fusion and related fields which illustrate the effectiveness of the approach. We also report on the status of a collaboration under way at Lawrence Berkeley National Laboratory between the Applied Numerical Algorithms Group (ANAG) and the Heavy Ion Fusion group to upgrade ANAG's mesh refinement library Chombo to include the tools needed by Particle-In-Cell simulation codes.
Date: November 4, 2003
Creator: Vay, J. L.; Colella, P.; Kwan, J. W.; McCorquodale, P.; Serafini, D. B.; Friedman, A. et al.
System: The UNT Digital Library
B physics at CDF (open access)

B physics at CDF

B physics is at the core of the CDF agenda for Run II. With the Tevatron performance gradually improving, samples of data corresponding to about 70 pb{sup -1} are now available. Due to improved detector capabilities these data already allow one to improve a number of Run I results, as well as perform a series of new measurements. We present an overview of the current state of B physics at CDF.
Date: June 4, 2003
Creator: Anikeev, K.
System: The UNT Digital Library
Mechanisms of Strontium and Uranium Removal from High-Level Radioactive Waste Simulant Solutions by the Sorbent Monosodium Titanate (open access)

Mechanisms of Strontium and Uranium Removal from High-Level Radioactive Waste Simulant Solutions by the Sorbent Monosodium Titanate

High-Level Waste (HLW) is a waste associated with the dissolution of spent nuclear fuel for the recovery of weapons-grade material. It is the priority problem for the U.S. Department of Energy's Environmental Management Program. Current HLW treatment processes at the Savannah River Site (Aiken, SC) include the use of monosodium titanate. The local structural speciation of sorbed U varied with loading but not for Sr. Sorbed Sr exhibited specific adsorption as partially-hydrated species whereas sorbed U exhibited specific adsorption as monomeric and dimeric U(VI)-carbonate complexes. Sorption proved site specific. These differences in site specificity and sorption mechanism may account for the difficulties associated with predicting Sr and U loading and removal kinetics using MST.
Date: November 4, 2003
Creator: Duff, M.C.
System: The UNT Digital Library
A new software package for computing the time-dependent aperture of the Auger Surface Detector (open access)

A new software package for computing the time-dependent aperture of the Auger Surface Detector

We describe a new general-purpose software package being developed for the Pierre Auger Collaboration for rapidly computing the differential and time-integrated apertures of regular arrays of surface detectors.
Date: June 4, 2003
Creator: Chou, Aaron S
System: The UNT Digital Library
Fermilab recycler stochastic cooling commissioning and performance (open access)

Fermilab recycler stochastic cooling commissioning and performance

The Fermilab Recycler is a fixed 8 GeV kinetic energy storage ring located in the Fermilab Main Injector tunnel near the ceiling. The Recycler has two roles in Run II. First, to store antiprotons from the Fermilab Antiproton Accumulator so that the antiproton production rate is no longer compromised by large numbers of antiprotons stored in the Accumulator. Second, to receive antiprotons from the Fermilab Tevatron at the end of luminosity periods. To perform each of these roles, stochastic cooling in the Recycler is needed to preserve and cool antiprotons in preparation for transfer to the Tevatron. The commissioning and performance of the Recycler stochastic cooling systems will be reviewed.
Date: June 4, 2003
Creator: Broemmelsiek, D. & Pasquinelli, Ralph
System: The UNT Digital Library
The Three Dimensional Thermal Hydraulic Code Bagira. (open access)

The Three Dimensional Thermal Hydraulic Code Bagira.

BAGIRA - a thermal-hydraulic program complex was primarily developed for using it in nuclear power plant simulator models, but is also used as a best-estimate analytical tool for modeling two-phase mixture flows. The code models allow consideration of phase transients and the treatment of the hydrodynamic behavior of boiling and pressurized water reactor circuits. It provides the capability to explicitly model three-dimensional flow regimes in various regions of the primary and secondary circuits such as, the mixing regions, circular downcomer, pressurizer, reactor core, main primary loops, the steam generators, the separator-reheaters. In addition, it is coupled to a severe-accident module allowing the analysis of core degradation and fuel damage behavior. Section II will present the theoretical basis for development and selected results are presented in Section III. The primary use for the code complex is to realistically model reactor core behavior in power plant simulators providing enhanced training tools for plant operators.
Date: May 4, 2003
Creator: Kalinichenko, S. D.; Kohut, P.; Kroshilin, A. E.; Kroshilin, V. E. & Smirnov, A. V.
System: The UNT Digital Library
Effects of Tritium in Elastomers (open access)

Effects of Tritium in Elastomers

A number of elastomers, used as flange gaskets in the piping system of the Savannah River Plant tritium facilities, are being examined to identify those compounds more radiation-resistant that the currently specified Buna-N rubber and to study the mechanism of tritium radiation damage. This paper discusses this study.
Date: March 4, 2003
Creator: Zapp, P.E.
System: The UNT Digital Library